Apparatus for forming a composite metallic preform tape

ABSTRACT

1. Apparatus for continuously producing metallic preform tape comprising: first supply means for providing a pair of substantially continuous metallic foils, each foil having an inner and an outer surface, means to move each for providing a plurality of substantially continuous filaments; means for aligning each of the filaments in a single plane disposed between the pair of metallic foils; means to move each of the filament at a given rate in the given direction; third supply means for providing at least one substantially continuous, plastically deformable, strippable film along at least one foil outer surface; means to move the film at the given rate in the given direction; and pressing means to press concurrently the film and foil toward and in contact with the filaments with a pressing force sufficient to deform plastically both the film and the foil around at least a portion of the filament outer surface.

Oct. 15, 1974 R.G..cARLsQN ETAL 3,841,942

APPARATUS FOR FORMING lA COMPOSITE METALLIC PREFORM TAPE Original FiledApril l2, 1971 United States Patent O U.S. Cl. 156-436 3 'ClaimsABSTRACT OF THE DISCLOSURE A composite metallic preform tape for use aslaminae in the manufacture of metallic composite articles is made from apair of metallic foils and high strength, high modulus filaments alignedbetween the foils. One form of the method involves first coating eitherthe foil inner surfaces or the filament outer surfaces, or both, with athin, nonmetallic adhesive bonding material which will decompose leavingsubstantially no residue upon heating at a temperature below that atwhich the foil and filaments will melt, and preferably below that atwhich they will bond together. The foil and the aligned filaments arethemselves aligned and, in a continuous form of the method, are moved atsubstantially the same rate and in the same direction so that the coatedsurface is between the foil and filaments. At the same time, the foiland filaments are pressed toward one another with a force sufficient toadhesively bond together the foil and filaments and to plasticallydeform the foil around at least a portion of substantially eachfilament.

In a preferred form, at least one plastically deformable, strippableouter film is applied for protection and, if desired, for a qualitycontrol record. Deformation of the foils arount at least a portion ofsubstantially each filament results in an article having a sandwichconstruction including centrally aligned filaments maintained in spacedapart relationship.

This is a divisional application of application Ser. No. 133,207 filedApr. 12, 1971, now U.S. Pat. No. 3,719,538, and assigned to the assigneeof the present invention.

BACKGROUND OF THE INVENTION This invention relates to a compositemetallic tape and, more particularly, to such a tape a plurality ofwhich are used as laminae in the manufacture of a metallic cornpositearticle. More specifically, such a tape is considered to be a preform inrespect to its ultimate use as an element of an article.

Requirements for strong lightweight metallic articles, particularly foruse in aerospace applications, has resulted in increasing developmentsin the area of fiber reinforced metallic composites. One method used inthe manufacture of composite articles involves the fabrication of thearticle from a plurality of reinforced sheets or tapes first stacked oneupon the other to build thickness. Then the article is provided bysubsequent pressing, heating, shaping, machining, grinding, etc. asrequired.

Such materials as aluminum, titanium and their alloys have been ofparticular interest as a matrix material for such composites because oftheir relatively low density. Reinforcement of such a matrix has beenprovided by high strength, high modulus filaments. One example is thefilament referred to as uncoated boron filament, generally involving atungsten filament substrate on which boron has been depositedpyrolytically. Another example is the so-called coated boron filamentinvolving further application of coatings, for example carbides,nitrides, etc. Other examples include filaments such as of siliconcarbide, carbon, graphite, A1203, etc.

3,841,942 Patented Oct. 15, 1974 The use of composite metallic materialfor the manufacture of articles has been shown to offer mechanicalproperty improvements such as strength and modulus in proportion to thematerials density when compared to homogeneous metal alloys, within thetemperature limitations of such material. It has been shown thatsignificant advantages can be attained by utilizing such propertyimprovements for a variety of mechanically loaded cornponents for jetengine and aircraft applications where the temperature environmentpermits the use of such composites.

One important facet in the fabrication of metal composite articles isthe type and condition of the sheet or tape forming the laminae of suchan article. The formation of a partially consolidated, thin tape permitsgreater latitude in forming such complex composite structures ascompressor vanes and blades. There have been reported several processesfor fabricating filament reinforced metallic tapes. These include theplasma spray application of matrix metal to the filaments, continuouscasting of the matrix metal around the filaments and the use of acentrally located carrier foil to carry multiple layers of filamentssandwiched between cover foils. However, such known processes presentproblems relating to thickness variations in the tape, requirements forhigher processing temperatures leading to property degradation andvariation, or relatively low volume percent of filament in the matrix.

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SUMMARY OF THE INVENTION It is a principal object of the presentinvention to provide an improved composite metallic tape by a methodlwhich provides a single layer of a plurality of aligned high strength,high modulus filaments in a sandwich construction to result in a highervolume percent of filaments in the matrix and an easily handled tape.

Another object is to provide a method for making such a tape as apreform tape which can be continuous rather than being inherentlybatch-type in nature.

Another object is to provide such a method with a means for protectingthe outer surface of the composite metallic tape while at the same timeproviding a quality control record of the position of the filamentswithin the composite metallic tape sandwich.

Still another object is to provide improved apparatus for manufacturingsuch a tape having an outer protective and quality control surface.

These and other objects and advantages will be more clearly understoodfrom the following detailed description, examples, and the drawingswhich are meant to be typical of rather than limiting on the scope ofthe present invention.

Brieiiy, the composite metallic tape, which is a preform in respect to asubsequently manufactured laminated article using such a tape, includesa single layer of a plurality of aligned high strength, high modulusfilaments bonded between the pair of metallic foils. The metallic foilsare plastically deformed around at least a portion of substantially eachfilament to secure the aligned filaments and to hold them spaced onefrom the other between the foils.

The method by which such a tape is made, in one preferred form, involvescoating either the inner surfaces of the foil or the outer surfaces ofthe filaments or both with a thin, non-metallic adhesive bondingmaterial which will decompose leaving substantially no residue uponheating at a temperature below that at which the foil and filaments willmelt and preferably below that at which they will bond together. Thenthe filaments, sandwiched and aligned between the foils, are pressedbetween the foils to bond the filaments within the foils through theadhesive bonding material and at the same time to plastically deform thefoil around at least a portion of substantially each filament outersurface.

One form of the method of the present invention involves the location ofa plastically deformable, strippable film on at least one foil outersurface prior to pressing so that the foil and film are pressed anddeformed together to protect the foil outer surface and to reproduce inthe film the foil deformation pattern.

Also, there is provided apparatus for continually producing the metallictape involving a pair of sources of substantially continuous metallicfoil, a substantially contnuous source of a plurality of alignedfilaments and at least one substantially continuous source of theplastically deformable strippable film, along with means to move suchfoil, filaments and film in the same given direction. In addition, theapparatus includes means to press concurrently the film and foil towardand in contact with the filaments with a force sufiicient to deformplastically both the film and the foil around at least a portion of thefilament outer surface.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an isometric, schematic viewof one form of the continuous method of the present invention;

FIG. 2 is a fragmentary, cross-sectional view of an assembly ofcomponents of the tape of the present invention prior to heating andpressing;

FIG. 3 is a fragmentary, cross-sectional view of one form of the preformtape of the present invention; and

FIG. 4 is a perspective, partially sectional -view of the tape of thepresent invention with the protective, replicating films partiallystripped away.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The roll bonding process of thepresent invention for producing composite metallic tape, and which hascontinuous capability, involves the disposition of aligned, highmodulus, high strength filaments, such as boron filaments or coatedboron filaments, between metallic foils to provide a sandwich structure.Such sandwich structure, having a single layer of filaments, ispreliminarily bonded through a heat decomposable and removablenou-metallic adhesive bonding material, for example, through theapplication of pressure and relatively low temperatures, to hold thesandwich structure together and to plastically deform the metallic foilsaround at least a portion of substantially each filaments outer surface.The method preferably includes the application of a strippable,plastically deformable (such as through the application of heat andpressure) lm to at least one foil outer surface to provide protectionfor such outer surface as well as to provide a relatively permanentquality control record of the filament distribution and alignment withinthe metallic composite tape. Such a filament/metal tape can beconsidered to be a preform in respect to its subsequent application aslaminae in the manufacture of composite metallic articles such as jetengine compressor blades and vanes.

One important feature of the present method in producing the compositemetallic tape of the present invention is the use of a relatively smallamount of a decomposable adhesive bonding material to hold together, ina tape preform sandwich, the single layer of aligned filaments between apair of metallic foils. An important characteristic of such a bondingmaterial is that it be capable of decomposing leaving substantially noresidue on heating at the relatively low temperatures contemplated inthe practice of the method of the present invention. Such a temperature,in any event, is below that at which neither the foil nor filaments willmelt. One type of such a bonding material which has been usedsuccessfully is acrylic resin in an organic solvent. Such resinsolutions are commercially available and are widely used in the brazingart to hold brazing powders together and in place on workpieces beingbrazed.

It should be understood that the adhesive bonding material can beapplied or carried by or with either the metallic foil or the filamentsor both depending upon the specific process and apparatus used. Forexample, in the continuous form of the process, the adhesive bondingmaterial can be applied in a thin film and preliminarily cured on rollsof the metallic foil. Also, the adhesive bonding material can be appliedto the filaments, such as prior to their introduction between themetallic foil to form the sandwich structure of the present invention.Alternatively the acrylic resin can be introduced as a separate sheet.For example, preparation of the filaments prior to introduction into themethod of the present invention can include the holding of the filamentsin alignment and on creels through a backing sheet of acrylic resin. Theacrylic resin then functions as the adhesive bonding material when it isintroduced into the method of the present invention between the metallicfoil.

Irrespective of the method of placement of the adhesive bonding materialbetween the foil inner surfaces and the outer surfaces of the filaments,it is most desirable to limit the amount of acrylic resin to thatnecessary to bond the pair of metallic foils with the single layer ofaligned filaments into the tape preform of the present invention. Inthis way, as little as possible of the bonding material will have to beremoved in subsequent fabrication operations utilizing the tape preformto manufacture laminated metallic composite articles.

The method of the present invention will be more clearly understood byreference to the drawing. FIG. 1 is an isometric, schematic view of oneform of the continuous method of the present invention including theapplication of a pair of plastically deformable strippable protectivefilms on the outside of the pair of metallic foils.

Tape preform 20 of the present invention, having a pair of outerstrippable protective films, is provided in FIG. 1 by disposing betweena pair of metallic foils 26 a plurality of aligned single or multiplearrays of filaments 22, for example, boron filaments of about 0.004diameter, from filament creels 24. For example, the filaments can bealigned in given direction D at a spacing of about filaments per inch.Metallic foils 26, which can be fed from rolls 28, in one form arealuminum or aluminum alloy foils, such as about 0.001 thick, precoatedwith a thin film of acrylic resin. Foils 26 also are aligned in givendirection D along with filaments 22.

In the preferred form .of the method of the present invention, aplastically deformable, strippable film 30, such as a heat shrinkablepolyethylene terephthalate film (one form of which is commerciallyavailable as Mylar plastic film) is located outwardly of the pair ofmetallic foils 26. Such a plastic film, for example, in the thicknessrange of about 0.0014103 is fed from rolls 32 aligned to deposit suchfilm 30 in given direction D. Mylar film has been found to beparticularly advantageous because of its relatively low temperatureplastic deformability or heat shrinkability and replicatabilitycharacteristics.

The composite sandwich structure, comprising a single layer of centrallylocated aligned filaments between a pair of metallic foils which in turnare sandwiched between strippable plastic film of the type described,and all of which are aligned in given direction D, are then fed betweenheated pressing rolls 34. Because of the nature both of the adhesivebonding material, when such materials as acrylic resins are selected,and the strippable protective and replicating film, when Mylar isselected, the rolls need be heated only at relatively low temperatures.Por example, they can be heated in the range of about 200-500" F. tosecure the components in the tape preform of the present invention. Thisrelatively low temperature represents a significant advantage over knowncompaction processes involving the application of temperature in therange of about 80G-1000" F.

The gap between pressing rolls 34 will affect the surface condition ofthe tape preform. Therefore, in the form of the invention shown in FIG.1, it is preferred that the gap be maintained at greater than a firstdistance which is the thickness of a filament plus the thickness of thepair of metallic foils, but less than a second distance which is thefirst distance plus the thickness of the protective or plastic films orfilms applied. With the preferred range of material dimensions, the gapwill be within the range of about .003".03.

In this way, with the heat of the rolls 34 sufficient to plasticallydeform or heat shrink the strippable film, pressure applied throughrolls 34 will result in little, if any, extrusion of metallic foil 26.However, it will cause the foil to deform plastically around at least aportion of the outer surface of the filaments to lock and to space thealigned filaments in position generally in given direction D. It shouldbe understood that the heat may be applied prior to press roll bonding.

During such rolling, film 30 acts as a pressure transmitting meanscapable of applying pressure substantially uniformly to metallic foil 26to deform it plastically about filaments 22 as has been described.Application of pressure to the adhesive bonding material holds togethermetallic foils 26 and filaments 22 into the tape preform of the presentinvention.

Because of the plastically deformable or heat shrinkable character ofthe strippable outer film 30, it can be easily removed from the foilouter surface 35 of the tape preform if desired. In the example shown inFIGS. l and 4, when two films 30 are applied, one can be stripped andsaved, such as on a film collector means as roll 36, as a qualitycontrol record. The other is left in place as a protective separatorbetween layers of the tape preform in the event it is either collectedand stored or shipped on tape preform roll 38, as shown in FIG. l, orcut into segments and stacked for storage or shipment. A processor canthen strip the remaining film 30 from the tape preform when it is used.This provides such processor with a quality control record duplicatingthat of the tape preform manufacturer.

With both protective films removed, the tape preform is ready forsubsequent fabrication into composite, laminated articles. This can beaccomplished through appropriate heat treatment and diffusion bondingprocedures which will remove the adhesive bonding material from betweenthe foils and filaments. For example, acrylic binder can be removed byheating for about l5 minutes at about 700 F. in vacuum. At the sametime, the stacked laminae are bonded into a reinforced compositearticle.

As was mentioned before, the volume percentage of filaments attainablethrough use of the tape preform of the present invention issignificantly higher than that attainable by known methods. Of course,the volume fraction of filaments will depend on the diameter of thefilament and the thickness of the foil. For example, with the filamentdiameters in the range of 0.004-0006, spaced in the range of about100-180 filaments per inch, in cooperation with metallic foil having athickness in the range of about 0001-0002", filament concentrations inthe range of about 40-50 volume percent are obtainable. However, it willbe understood that other thicknesses, diameters and spacing can beselected. The preferred tape thickness range for practical fabricationis about 0.003-0.02" utilizing metal foils of about 0001-0005 thick witha lament diameter of about 0.003-0.008.

Although the filaments generally are ofv the same material, it will beunderstood that various types of filaments can be intermixed as desiredto attain the properties selected for the final product. In addition, ifdesired, filaments of the same material as the foil can be included inorder to provide additional spacing between filaments or to adjust tapedensity.

One specific example in which a tape of the present invention was madeto a width of about 6" used a pair of 0.001 thick foils of an aluminumalloy, commercially available as 2024 aluminum alloy, precoated with anacrylic cement. The filaments were aligned boron filaments having adiameter of about 0.004" at a spacing of about 0.0062 inch. A pair of0.0015 thick Mylar films -were applied as described above. Prior tocontinuous roll pressing while heating at a temperature of about 300 F.,the assembly of components appeared as in FIG. 2, which is a fragmentarycross-sectional view of an assembly of the components of the tape of thepresent invention prior to pressing and heating. Adhesive bondingmaterial 40 which preferably is an acrylic cement is, in this example,carried by foil inner surface 42 and positioned in contact with aportion of outer surfaces 44 of filament 22. However, it will beunderstood that such bonding material can be placed in contact with boththe foil inner surfaces 42 and the filament outer surfaces 44 by avariety of means including the coating of filaments 22 or thepositioning of a separate resin film bet-Ween the filaments and thefoils. As shown in FIG. 2, a pair of plastically deformable, strippablefilms 30 such as of Mylar are positioned to sandwich therebetween theother components of the assembly.

After pressing to compact the assembly of FIG. 2 and to plasticallydeform the foil around at least a portion of substantially each filamentouter surface, there is provided one form of the tape of the presentinvention as shown in FIG. 3. In the fragmentary, sectional view of FIG.3, after pressing, the foils 26 are plastically deformed around at leasta portion of substantially each filament outer surface, thus securing insubstantially spaced apart relationship the aligned filaments 22.Conforming to the outer configuration of foils 26 are the protective andreplicating strippable films 30 covering the lateral portions or foilouter surfaces 35 of the tape of the present invention.

In the apparatus form of the present invention, a motor 46 in FIG. 1 canbe operably connected with pressing rolls 34 to drive the rolls in givendirection D as shown by arrows 48. When the filaments 22 and pair offoils 26 are fed into the gap between rolls 34, optionally along withprotective and replicating film 30, the filament from creels 24, thefoil from rolls 28 and the film from rolls 32 are moved at substantiallythe same given rate in the given direction D. To facilitate suchrotational movement, the various rolls and creels can be journaled toallow free rotation. Optionally, tensioning devices can be placed inappropriate positions as desired. Alternatively, each of the rolls andcreels can be rotated or moved separately such as by separate motorseach coordinated with the others to provide appropriate movement ingiven direction D.

Rolls 34, are shown in FIG. l to be mounted in a press 50 so that theroll gap and pressure applied as shown by arrows P can be adjusted in amanner well known in the art. In addition, rolls 34 can be heated, suchas by resistance heaters mounted within the rolls and adjustablycontrolled such as by thermostats or thermocouples.

What is claimed is:

1. Apparatus for continuously producing metallic preform tapecomprising:

first supply means for providing a pair of substantially continuousmetallic foils, each foil having an inner and an outer surface;

Imeans to move each of the pair of foils at a given rate in a givendirection;

second supply means for providing a plurality of substant-iallycontinuous filaments;

means for valigning each of thefilaments in a single plane disposedbetween the pair of metallic foils; means to move each of the filamentsat a given rate in the given direction;

third supply means for providing at least one substantially continuous,plastically deformable, strippable lm along at least one foil outersurface;

'means to move the tflm at the given rate in the given direction; and

pressing means to press concurrently the film and foil toward and incontact with the filaments with a pressing force sui-cient to deformplastically lboth the lm and the foil around at least a portion of thefilament outer surface.

2. The apparatus of claim 1 including, in addition, means to apply heatto the -lrn and foil, the heat being applied at a temperature less thanthat which will melt the lowest to melt of the foil and film.

3. The apparatus of claim 1 in which:

the third supply means is a pair of rolls of the lm;

lthe apparatus including, in addition, lm collector means to collect oneof the pair of -strippable films from a foil outer surface.

References Cited UNITED STATES PATENTS 12/1969 10/1950 2/1966 3/1966 8/1972 11/1971 lll/1969 S/1973 Marcell 156--436 Landgraf 156-323 Traut156-323 Bohannon, Jr. 156436 Rogosch et al. 156-179 Lemelson 156-384'Frigstad 16l-144 Schurb 161-143 D. I. FRITSCH, Primary Examiner

1. Apparatus for continuously producing metallic preform tapecomprising: first supply means for providing a pair of substantiallycontinuous metallic foils, each foil having an inner and an outersurface, means to move each for providing a plurality of substantiallycontinuous filaments; means for aligning each of the filaments in asingle plane disposed between the pair of metallic foils; means to moveeach of the filament at a given rate in the given direction; thirdsupply means for providing at least one substantially continuous,plastically deformable, strippable film along at least one foil outersurface; means to move the film at the given rate in the givendirection; and pressing means to press concurrently the film and foiltoward and in contact with the filaments with a pressing forcesufficient to deform plastically both the film and the foil around atleast a portion of the filament outer surface.